Channel Estimation Using Averaging and Interpolation

1. A method of performing channel estimation, comprising: receiving a frame comprising, for each subcarrier of a subset of subcarriers in the frame, a pair of time-adjacent pilot symbols in the subcarrier, wherein the subcarriers of the subset are regularly spaced apart from one another in the frequency domain, wherein a first subsequent pair of time-adjacent pilot symbols is in an increasing frequency order for a first frequency range; generating time-averaged channel estimates for each subcarrier of the subset based on the pairs of time-adjacent pilot symbols; generating frequency-averaged channel estimates for respective subcarriers based on the time-averaged channel estimates; and interpolating between respective frequency-averaged channel estimates to generate interpolated channel estimates for subcarriers between the respective subcarriers; wherein: the frame comprises an orthogonal frequency-division multiple-access (OFDMA) frame comprising multiple frame portions corresponding to respective transmitting devices; each of the multiple frame portions comprises, for each subcarrier of a subset of subcarriers in the frame portion, a pair of time-adjacent pilot symbols, the pairs of time-adjacent pilot symbols being regularly spaced in the frequency domain within the frame portion, wherein a second subsequent pair of time-adjacent pilot symbols is in a decreasing frequency order for a second frequency range; and the method further comprises repeating generating the time-averaged channel estimates, generating the frequency-averaged channel estimates, and interpolating between respective frequency-averaged channel estimates for each of the multiple frame portions.

2. The method of claim 1 , wherein the multiple frame portions comprise non-overlapping, contiguous groups of subcarriers.

3. The method of claim 1 , wherein the pairs of time-adjacent pilot symbols comprise pairs of pilot symbols in adjacent orthogonal frequency-division multiplexing (OFDM) symbols.

4. The method of claim 3 , wherein the pairs of pilot symbols have a staggered spacing in the time domain, the method further comprising de-staggering the pairs of pilot symbols.

5. The method of claim 1 , further comprising: performing pilot matching for the pilot symbols; and generating channel estimates corresponding to the pilot symbols, based on the pilot matching; wherein generating the time-averaged channel estimates comprises averaging channel estimates corresponding to respective pairs of the time-adjacent pilot symbols.

6. The method of claim 5 , wherein generating the channel estimates corresponding to the pilot symbols comprises performing time-domain least-squares channel estimation.

7. The method of claim 1 , wherein generating the frequency-averaged channel estimates comprises, for a respective subcarrier having two adjacent subcarriers, averaging time-averaged channel estimates for the two adjacent subcarriers.

8. The method of claim 1 , wherein generating the frequency-averaged channel estimates comprises replacing time-averaged channel estimates for respective subcarriers with frequency-averaged channel estimates for the respective subcarriers.

9. The method of claim 1 , wherein generating the frequency-averaged channel estimates comprises using a sliding frequency window to specify subcarriers for which respective time-averaged channel estimates are to be averaged.

10. The method of claim 1 , wherein: generating the frequency-averaged channel estimates comprises performing oversampling; the interpolating is performed over oversampled frequencies; and the method further comprises down-sampling results of the interpolating.

11. The method of claim 1 , wherein the interpolating comprises performing linear interpolation between respective frequency-averaged channel estimates.

12. The method of claim 1 , wherein generating the time-averaged channel estimates comprises generating a time-averaged channel estimate for an edge subcarrier, the method further comprising: retaining the time-averaged channel estimate for the edge subcarrier; and interpolating between the time-averaged channel estimate for the edge subcarrier and a frequency-averaged channel estimate for another subcarrier, to generate an interpolated channel estimate.

13. The method of claim 12 , wherein: the frame is an OFDMA frame; and the edge subcarrier is at an edge of a group of contiguous subcarriers assigned to a respective transmitting device.

14. A communications device, comprising: a transceiver to receive a frame comprising, for each subcarrier of a subset of subcarriers in the frame, a pair of time-adjacent pilot symbols in the subcarrier, wherein the subcarriers of the subset are regularly spaced apart from one another in the frequency domain, wherein a first subsequent pair of time-adjacent pilot symbols is in an increasing frequency order for a first frequency range; one or more processors; and a memory storing one or more programs configured for execution by the one or more processors, the one or more programs comprising: instructions to generate time-averaged channel estimates for each subcarrier of the subset based on the pairs of time-adjacent pilot symbols; instructions to generate frequency-averaged channel estimates for respective subcarriers based on the time-averaged channel estimates; and instructions to interpolate between respective frequency-averaged channel estimates, to generate interpolated channel estimates for subcarriers between the respective subcarriers; wherein: the frame comprises an OFDMA frame comprising multiple frame portions corresponding to respective transmitting devices; each of the multiple frame portions comprises, for each subcarrier of a subset of subcarriers in the frame portion, a pair of time-adjacent pilot symbols, the pairs of time-adjacent pilot symbols being regularly spaced in the frequency domain within the frame portion, wherein a second subsequent pair of time-adjacent pilot symbols is in a decreasing frequency order for a second frequency range; and the one or more programs further comprise instructions to repeat generating the time-averaged channel estimates, generating the frequency-averaged channel estimates, and interpolating between respective frequency-averaged channel estimates for each of the multiple frame portions.

15. The communications device of claim 14 , wherein: the pairs of time-adjacent pilot symbols comprise pairs of pilot symbols in adjacent OFDM symbols and have a staggered spacing in the time domain; and the one or more programs further comprise instructions to de-stagger the pairs of pilot symbols.

16. The communications device of claim 14 , wherein the instructions to generate the frequency-averaged channel estimates comprise instructions to specify subcarriers for which respective time-averaged channel estimates are to be averaged using a sliding frequency window.

17. The communications device of claim 14 , wherein: the instructions to generate the frequency-averaged channel estimates comprise instructions to perform oversampling; and the instructions to interpolate comprise instructions to perform interpolation over oversampled frequencies and to down-sample results of the interpolation.

18. The communications device of claim 14 , wherein: the instructions to generate the time-averaged channel estimates comprise instructions to generate a time-averaged channel estimate for an edge subcarrier; and the one or more programs further comprise instructions to interpolate between the time-averaged channel estimate for the edge subcarrier and a frequency-averaged channel estimate for another subcarrier, to generate an interpolated channel estimate.

19. A non-transitory computer-readable storage medium storing one or more programs configured to be executed by one or more processors in a communications device, the one or more programs comprising: instructions to generate time-averaged channel estimates for each subcarrier of a subset of subcarriers in a frame based on respective pairs of time-adjacent pilot symbols in the subset, wherein each subcarrier of the subset comprises a respective pair of time-adjacent pilot symbols and the subcarriers of the subset are regularly spaced apart from one another in the frequency domain, wherein a first subsequent pair of time-adjacent pilot symbols is in an increasing frequency order for a first frequency range; instructions to generate frequency-averaged channel estimates for respective subcarriers based on the time-averaged channel estimates; and instructions to interpolate between respective frequency-averaged channel estimates, to generate interpolated channel estimates for subcarriers between the respective subcarriers; wherein: the frame comprises an OFDMA frame comprising multiple frame portions corresponding to respective transmitting devices; each of the multiple frame portions comprises, for each subcarrier of a subset of subcarriers in the frame portion, a pair of time-adjacent pilot symbols, the pairs being regularly spaced in the frequency domain within the frame portion, wherein a second subsequent pair of time-adjacent pilot symbols is in a decreasing frequency order for a second frequency range; and the one or more programs further comprise instructions to repeat generating the time-averaged channel estimates, generating the frequency-averaged channel estimates, and interpolating between respective frequency-averaged channel estimates for each of the multiple frame portions.

20. The non-transitory computer-readable storage medium of claim 19 , wherein: the pairs of time-adjacent pilot symbols comprise pairs of pilot symbols in adjacent OFDM symbols and have a staggered spacing in the time domain; and the one or more programs further comprise instructions to de-stagger the pairs of pilot symbols.

21. The non-transitory computer-readable storage medium of claim 19 , wherein the instructions to generate the frequency-averaged channel estimates comprise instructions to specify subcarriers for which respective time-averaged channel estimates are to be averaged using a sliding frequency window.

22. The non-transitory computer-readable storage medium of claim 19 , wherein: the instructions to generate the frequency-averaged channel estimates comprise instructions to perform oversampling; and the instructions to interpolate comprise instructions to perform interpolation over oversampled frequencies and to down-sample results of the interpolation.

23. The non-transitory computer-readable storage medium of claim 19 , wherein: the instructions to generate the time-averaged channel estimates comprise instructions to generate a time-averaged channel estimate for an edge subcarrier; and the one or more programs further comprise instructions to interpolate between the time-averaged channel estimate for the edge subcarrier and a frequency-averaged channel estimate for another subcarrier, to generate an interpolated channel estimate.

24. A communications device, comprising: means for receiving a frame comprising, for each subcarrier of a subset of subcarriers in the frame, a pair of time-adjacent pilot symbols in the subcarrier, wherein the subcarriers of the subset are regularly spaced apart from one another in the frequency domain, wherein a subsequent pair of time-adjacent pilot symbols is in an increasing frequency order for a first frequency range; means for generating time-averaged channel estimates for each subcarrier of the subset based on the pairs of time-adjacent pilot symbols; means for generating frequency-averaged channel estimates for respective subcarriers based on the time-averaged channel estimates; and means for interpolating between respective frequency-averaged channel estimates to generate interpolated channel estimates for subcarriers between the respective subcarriers; wherein: the frame comprises an orthogonal frequency-division multiple-access (OFDMA) frame comprising multiple frame portions corresponding to respective transmitting devices; each of the multiple frame portions comprises, for each subcarrier of a subset of subcarriers in the frame portion, a pair of time-adjacent pilot symbols, the pairs of time-adjacent pilot symbols being regularly spaced in the frequency domain within the frame portion, wherein a second subsequent pair of time-adjacent pilot symbols is in a decreasing frequency order for a second frequency range; and the communications device further comprises means for repeating generating the time-averaged channel estimates, generating the frequency-averaged channel estimates, and interpolating between respective frequency-averaged channel estimates for each of the multiple frame portions.

25. The communications device of claim 24 , wherein: the pairs of time-adjacent pilot symbols comprise pairs of pilot symbols in adjacent OFDM symbols and have a staggered spacing in the time domain; and the communications device further comprises means for de-staggering the pairs of pilot symbols.

26. The communications device of claim 24 , further comprising means for using a sliding frequency window to specify subcarriers for which respective time-averaged channel estimates are to be averaged.

27. The communications device of claim 24 , wherein: the means for generating time-averaged channel estimates comprises means for generating a time-averaged channel estimate for an edge subcarrier; and the communications device further comprises means for interpolating between the time-averaged channel estimate for the edge subcarrier and a frequency-averaged channel estimate for another subcarrier, to generate an interpolated channel estimate.